Removal of paints and paint-like deposits is an old and well-developed art. Generally the objective is to soften the deposit, usually by at least partially dissolving it so that it can be scraped away. The intended effect is usually that of dissolving the material so it becomes fluid. The result is generally a softening of the deposit accompanied by some liquids. The difficulty of pursuing this softened material into cracks and structural intersections is well-known. One response to this problem is to dip the object into a tank of stripper and let it dissolve away.
Not only are these techniques very troublesome, but disposition of the stripper and of its contents is becoming more of an environmental problem. Generally, these strippers use strong organic solvents which, in addition to their disposal problems, constitute a potential health hazard to the user, to the environment, and to the substrate structure.
Despite these inherent problems, because they represent the best materials available, these materials are regularly used on durable, non-porous surfaces that can be regarded as "hard". Examples are the stripping of wood, and the cleansing of metal and enamel surfaces, subject to other problems discussed below.
However, they are not suitable for porous materials such as concrete, concrete block, stucco, cinderblock, rocks and stone, bricks and trees. This is because the dissolved and softened material tends to enter the porous surface, from which it can be removed only partially and then only with great difficulty, and usually with damage to the surface. When the material flows into the pores, later attempts to flush it out can be expected to drive at least some of it deeper. Attempts are sometimes made to overcome this problem by attacking the surface with a strong water jet, often with sandblast grits in it, or by sandblasting. This leaves modified areas which frequently have faint patterns of what was removed.
Soft surfaces, such as vinyls cannot withstand the action of these strippers, or of sandblasts. Neither can many delicate surfaces, for example plexiglass, where the plexiglass will be rendered translucent, rather that transparent.
Further, especially on large exposed areas such as retaining walls and highway signs, if this dissolved material is flushed from the surface, nearby areas will be contaminated by it. As a consequence, organizations such as the California Department of Transportation and many municipal entities simply cover graffiti with a patch of paint, leaving the deposits in place. A trip along many streets and freeways will disclose those patches, whose only merit is that they are less objectionable than what they cover.
Further, even as to enamelled highway signs, where there is no penetration into the sign itself, the action of strippers is slow. While their action could be accelerated by the use of hot water, hot solvents, steam, and sandblasting, highway crews cannot carry along with them such equipment, which often must reach to very inconvenient places. Again, the run-off is itself objectionable, especially after the solvents evaporate.
In an attempt to frustrate graffiti artists, it has become common practice to place a rather expensive layer of plastic material such as 3M 1150 on enamel signs or to impregnate the signs with laminate at the time of manufacture. Unfortunately these respond poorly to solvents applied hot, such as MEK and Kerosene, and even the new citrus-based solvents. Generally these tend to attack the laminations, often delaminating them, resulting in cracking and migration through the plastic to the sign surface. The inherent problem in solvents such as these is that their primary intended effect is to dissolve the adherent material. When quick dissolving of such deposits is intended, it is not surprising that at least some damage will be done to the substrates because of these "hot" solvents.
What is needed, and what this invention provides, is a biodegradable cleanser, which can be extended with water, which works quickly and well at ambient temperatures, which primarily does not dissolve the substances being removed (although in some circumstances some solution may occur), whose effluent is principally a solid that is not itself objectionable, and which can be flushed away with water or wiped up with a cloth, or gathered with a squeegee. For large areas, removal by small volumes of high pressure jets of water will be preferred. All of these methods leave the surface cleansed of the deposit.
It is another object of this invention to provide a method for removing the subject deposits from surfaces, which method produces an effluent that often is agreeably left where it drains next to the surface which was cleansed. It does not itself become a disposal problem. In fact, often it can be swept up, raked up, or simply covered up with dirt. The composition is biodegradable.
It is still another object of this invention to provide a cleanser and a method in which the principal mechanism for removal of the deposit is interruption of its physical bond with the surface, followed primarily by removal of the material in a solid condition. Often it is particulate, but in other circumstances it may form a soft layer which can be gathered up as stated above.
Yet another object of this invention is to provide a more affordable cleanser, both in its inherent cost and in the elimination of damage to cleansed surfaces. Known stripper type compositions tend to use expensive organic solvents, sometimes for their own action, and sometimes as a carrier for other components. They themselves frequently damage the surface to be cleansed. No other carrier can be less expensive than water, which this cleanser can use. Furthermore this invention enables the use of a group of components some of which, if used alone, could frustrate the intended action. For reasons which are presently not fully understood, the combination is more benign, resulting in little or no dissolving of the deposits. Used alone, these components vigorously attack and dissolve paints and paint-like deposits. The combination of ingredients provided by this invention attains the intended results with them, but cause no, or at most minimal, damage to the substrate.
The so-called "green" solvents in general do not work as well as the products of this invention, and are considerably more expensive. While using relatively inexpensive components, the formulations of this invention are safe for the user, safe for the environment, safe for the surface, are biodegradable, and when extended by a carrier, can use water and thereby be water-based.